1. Field of the Invention
The present invention relates a method and apparatus that remains onboard a semi tractor trailer vehicle for automatically adjusting an axle's alignment under dynamic conditions.
2. Description of Prior Art
Axle alignment of a tractor trailer vehicle is currently set at the factory and can only be adjusted by a technician by loosening the axle adjustment mechanism, measuring, adjusting, and re-tightening the mechanism. Various techniques are used in the field for checking and correcting axle alignment, but all of these techniques are performed by a technician with the vehicle in a static position. There are currently no provisions for accurately monitoring axle movement or alignment or for dynamically adjusting a tractor trailer axle while the vehicle is in motion.
The alignment of drive or trailer axles in a tandem configuration is extremely critical to the proper tracking of the vehicle. The correct alignment of a tandem axle configuration is when both axles are parallel to one another and both axles are perpendicular to the vehicle's geometric centerline (a line determined through the midpoint of the rear axle and intersecting the midpoint of the front axle).
There are basically two types of tandem axle misalignment; one is referred to as tandem thrust angle (the angle between the longitudinal center plane and the geometrical axis). Thrust angle occurs when the tandem axles are parallel, but not perpendicular to the vehicle's centerline. In this case, the tandem axles push the vehicle away from the normal direction of vehicle travel.
The other is referred to as tandem scrub angle, which occurs when the tandem axles are not parallel. In this case, the driver must turn the front wheels to offset the push of the tandem axles in order to keep the vehicle moving straight ahead. This causes a scrub effect on every tire on the vehicle.
It is well known in the industry that tandem axle misalignment of the tractor and/or trailer can cause problems such as safety, decrease in fuel mileage, vehicle vibration, higher maintenance cost, driver fatigue from poor handling characteristics of the vehicle, excessive premature tire wear, and an increase in tire temperature. Tire temperature may be a contributing factor for the rapid disintegration of the tire's tread which is hazardous and often seen laying along the roadway.
Most axle alignment problems are unseen to the eye. Because of this fact it is possible to overlook alignment problems that might exist with the axles for a long period of time, since many of these problems will take several hundred to even thousands of miles to manifest themselves and become a contention to the driver.
Conclusion—Prior Art
After observing prior axle alignment techniques, it becomes apparent that there is still a need to have an apparatus onboard a tractor trailer vehicle that will monitor an axle's normal path of movement and dynamically adjust the axle back to the predetermined path while the vehicle is in motion. Still a further need is for an apparatus that allows repeatable repositioning of the axle's alignment under dynamic and adverse road conditions. A still further need is for an apparatus and method which will detect deviation of a particular side of a particular axle, and convey signals to a mechanical actuating device which will dynamically realign the deviated axle back to a normal path of movement.